Digital broadcast communication systems such as DVB-H (Digital Video Broadcasting—Handheld), DVB-T (Digital Video Broadcasting—Terrestrial) or other client-server communication system, enable end users to receive digital content including video, audio, and data. Using a fixed or mobile terminal, a user may receive digital contents over a cable or wireless digital communication network. For example, a user may receive data such as a broadcast program in a data stream. Additional data associated with the broadcast program such as interactive multimedia contents including program title, news, interactive services, or additional audio, video and graphics, may also be available. The interactive multimedia contents can be previously stored at the server or generated during the broadcasting or multicasting of the program.
Interactive multimedia content is a service that aggregates interactive services with a conventional A/V broadcasting service. MPEG-4 Part 20 designates interactive multimedia using the terms ‘rich media’. OpenTV and DVB designate interactive multimedia using the terms ‘interactive television’. The core idea of interactive multimedia is adding one or more interactive multimedia to an original A/V stream. The content of the interactive multimedia, usually synchronized with the original A/V stream, will enable reaction to different user inputs. The processing of user inputs can be either handled locally or remotely, in the latter case using a bi-directional channel.
The content of the interactive multimedia service is a collection of multimedia data, such as graphics, text, audio and video etc, which may change over time based on the A/V stream. The A/V stream has its own timeline, here, the timeline is a term used to describe that a video/audio sequence is ordered by time stamp. The corresponding contents of interactive multimedia content also have a timeline, which relates to this A/V stream timeline by a reference, such as a start point tag. That is, there is a temporal synchronization between the corresponding interactive multimedia content and the A/V stream. The start point tag refers the specific time point of the timeline of A/V stream. When the A/V stream plays to the specific time point, an event is triggered to play the corresponding interactive multimedia contents.
The interactive multimedia contents are shown according to users input during a specific period of timeline of A/V stream. For example, a sports TV (television) channel may be associated with a pop-up interactive multimedia content that describes an athlete who just scored a goal and the video scene of the athlete is being broadcasted. When the video scene of the program changes, the other interactive multimedia contents will be used accordingly. The transmitted interactive multimedia content can be either integrally multiplexed into conventional A/V stream or sent in a separate channel.
According to the above, interactive multimedia services can be an interactive experience during a specific period of the A/V stream between a multimedia server such as a service providing device and the end users. During the specific period users may send requests for a type of interactive multimedia to the service providing device, and then the service providing device will send the requested multimedia content to the users. However, the bandwidth resource used by interactive multimedia services for multimedia requesting and multimedia delivery during the specific period will not scale well with growing numbers of users. This may be the case for a multicasting communication environment or a broadcasting TV network with return channel.
Therefore, an improved method for requesting and delivering interactive multimedia content is needed.